A-10C Yaw-Roll coupling

Dear DCS users and tech support!

I am a real world pilot and have flown the Dash-8 and the Learjet60xr.

As I have noticed the yaw to roll coupling is very strong when the rudder is input, e.g. when an engine fails to correct for yaw.

This is by far too extrem as the airplane will snap roll like a biplane in aerobatic flight.

In real world even if the incorrect rudder is pushed (not dead foot dead engine, but the opposite rudder) then the airplane will yaw to the incorrect direction to counter for engine thrust moment but the airplane will almost not start to roll away.

Is there a cure for this problem (settings?)

Kind regards

Daniel

I'm not sure I understood entirely what the problem is, but remember the A-10C uses SAS. Try disabling it and see if the airframe behaves as you expect.

Only an A10 pilot could confirm the realness, but Ive always understood thats a bi product of the high wide engines couples with hugh control surfaces. Its unique and challenging, but managable imo.

I thought it was strange too. I've never flown the A-10 IRL, but I flew the C-2A which has even bigger vertical stabilizers, and even an extreme amount of yaw didn't cause that much residual roll. Could it be that abrupt or extreme rudder causes instability that is being compensated by SAS by adding roll in an attempt to stabilize? In the same line of inquiry; could it be that since SAS binds auto rudder to roll, that the code is erroneously causing this to happen in the inverse (roll is bound to yaw as yaw is bound to roll)?

I know I have been warned multiple times for comparing combat aircraft to airliners and GA planes.

I am frequently told that GA and civil planes are designed docile and nose heavy allowing high positive stability, easy to trim, along with low coupling etc. (Don't both the Dash-8 and Learjet have yaw dampers to help them anyway?).

Most combat aircraft are on a knife edge with neutral to rearward balance to get high pitch and roll instability for maneuvering. This is so much the case with modern fighters that it's impossible to fly them without the computer stabilization. The A10 can be flown with out it, but the coupling is even greater and I believe I read somewhere that is a 'feature' of the air frame.

Never tried to snap roll it in the Sim, but it will pull out of a dive at 6g and it will spin ... eventually and self right with hands off... usually.

However... isn't a snap roll induced by back pitch to the point of high speed/high alpha stalling it usually resulting in a hard roll/yaw one way or other? Similarly to a normal vertical spin the rudder is only used to induce the yaw so it spins in the direction you want rather than randomly? Then ... that's what the "Performance limits" beep is all about. If you get a constant tone, you are at alpha limits, if you get a rapid beeping and keep pulling it snaps on you, if you are very aggressive and very slow it will spin on you.

But I don't have any real life facts to back it up.

It cannot be true that the aircraft violently rolls when only a litte ruder is applied for final approach heading corrections to align the aircraft to runway heading. In no means this is a realistic value. It should be reduced like the shaking of the helicopter was reduced in UH-1 Huey simulation to be more realistic. I also have flown Jetrangers and never have seen a Behaivor like in the simulation, thus it was the right decision to reduce the effect.

The other thing is that the aircraft does violently roll with a rudder deflection by the rudder (pedals=stick input) but does not roll when there is a rudder trim set via the rudder trim knob. So it cannot be real!

It does seem a bit violent, however for me the behavior is pretty similar when trimming. 2-3 ticks of trim will cause the aircraft to roll fairly strong and is comparable to a very light touch of the rudder with similar rudder deflection.

This is with SAS engaged as you can't(?) trim yaw otherwise. The reaction to rudder input stays the same though, SAS engaged or not.

No idea how a real A-10 behaves though - might be a question worth asking an A-10 pilot though:

http://forums.eagle.ru/showthread.php?t=157896

http://forums.eagle.ru/showthread.php?t=165077

Does seem excessive and I too would be interested in hearing from an a-10 pilot. The fact that the twin vertical stabilisers cover such a large area combined with the a-10s thick high-lift low-taper wing structure would however create a greater roll effect than the conventional airliner due to greater outboard lift in the yaw.

If you want to find truth you can find A-10A flight manual, "Departures" paragraph. There you can find a reaction to full rudder.

This wasn't really about full rudder more like slight rudder flipping the aircraft upside down.

The funny thing is though now that I tried it again it feels more gradually than before - not sure why, but then I didn't really document it the first time...

I'm suspecting this is a controller sensitivity issue, not a simulation modeling issue or it would happen to everyone.

Check your controller sensitivity and null zones. In most aircraft, rudder should affect yaw at least a little bit. Some aircraft will produce positive roll, some will produce inverse roll. Flipping over though with only rudder input? That I have not seen. If you are using a twist grip controller, use your desktop control panel and operate all your axis though full motion and in combinations. Perhaps your controller motions are driving your other axis out of their null zones.

-Pv-

I had a similar problem after one of the upgrades. The controller setup was all screwed up. The overlap of rudder assignments made it almost impossible to fly. I was fighting it the whole time wondering what the hell was going on. So do check the controller assignment to rule it out.